I discovered that the stack-smashing protection options
(-fstack-protector and friends) were rejected on nios2 because this
backend wasn't defining FRAME_GROWS_DOWNWARD. There doesn't seem to be
any particular reason not to enable that, so here I've switched it on.
Committed after regression testing on nios2-linux-gnu. I've also got
this working for nios2-elf on a local branch in conjunction with BSP
library support and this patch
https://gcc.gnu.org/ml/gcc-patches/2017-10/msg00537.html
which is still awaiting review.
-Sandra
2017-10-28 Sandra Loosemore <san...@codesourcery.com>
gcc/
* config/nios2/nios2.h (FRAME_GROWS_DOWNWARD): Define to 1.
* config/nios2/nios2.c (nios2_initial_elimination_offset): Make
FRAME_POINTER_REGNUM point at high end of local var area.
diff --git a/gcc/config/nios2/nios2.h b/gcc/config/nios2/nios2.h
index 420543e..9fdff02 100644
--- a/gcc/config/nios2/nios2.h
+++ b/gcc/config/nios2/nios2.h
@@ -252,6 +252,7 @@ enum reg_class
/* Stack layout. */
#define STACK_GROWS_DOWNWARD 1
+#define FRAME_GROWS_DOWNWARD 1
#define FIRST_PARM_OFFSET(FUNDECL) 0
/* Before the prologue, RA lives in r31. */
diff --git a/gcc/config/nios2/nios2.c b/gcc/config/nios2/nios2.c
index cdd5e9a..5c70de7 100644
--- a/gcc/config/nios2/nios2.c
+++ b/gcc/config/nios2/nios2.c
@@ -1114,7 +1114,9 @@ nios2_initial_elimination_offset (int from, int to)
switch (from)
{
case FRAME_POINTER_REGNUM:
- offset = cfun->machine->args_size;
+ /* This is the high end of the local variable storage, not the
+ hard frame pointer. */
+ offset = cfun->machine->args_size + cfun->machine->var_size;
break;
case ARG_POINTER_REGNUM:
